Patent GB-951549-A (GB)
Title: Improvements in or relating to vapourpermeable films and coatings
IPC: D06N3/10
Filed: 1961-05-15
Abstract: Vapour-permeable microporous films and coatings are produced by forming a film or coating of a water-insoluble copolymer containing carboxyl groups on the polymer chain, with or without a proportion of a vinyl chloride polymer or a polyurethane elastomer which may exceed the proportion of the co-polymer, from a solution of the copolymer (and other polymer if employed) in a water-miscible solvent therefor, the solution containing also an oxide of a polyvalent metal, bathing the film or coating with water or an equivalent inert liquid to coagulate the copolymer and remove the solvent, and curing and drying the film or coating produced.  The solution of the copolymer may also contain sulphur. The copolymer may be derived from two or more monomers, at least one of which is a conjugated diene having 4-9 carbon atoms in the molecule, and at least one of which is a carboxylic acid containing ethylenic unsaturation at which polymerization can take place.  The copolymer may be a rubber ter-polymer of a butadiene-1,2-hydrocarbon, acrylonitrile or a substituted acrylic nitrile, or acrylic acid or a homologue or a -substitution product thereof. The solution may contain a vinyl chloride polymer in a weight ratio to the copolymer of up to 50:50. The solution may be brought to the verge of gelling before mixing it with water or an equivalent inert liquid.  The solution may be applied as a coating to a substrate of a flexible porous fibrous material or of a smooth surfaced impervious material.  In the latter case to form a film which is subsequently stripped from the film support.  The copolymer in the film or layer may be partially cured by heating with water or an equivalent inert liquid to a temperature above normal room temperature. The copolymer may contain residual unsaturation and the solution may contain sulphur and after partial curing the film or coating may be heated until the copolymer is fully cured.  An "equivalent" inert liquid is defined as one which is (a) a non-solvent for the copolymer and any other polymer which may be present in the solution; (b) miscible with water and the organic solvent in which the copolymer is dissolved; (c) chemically inert to all the constituents of the film-forming solution at the bathing temperature. Examples of suitable liquids are ethylene glycol, glycerol, glycol monoethyl ether, hydroxyethyl acetate, and water-miscible alcohols such as t-butyl alcohol.  The preferred polyvalent metal oxide is zinc oxide, but oxides of calcium, magnesium, tin, dibutyl tin, lead, barium, cobalt or strontium known to be suitable for cross-linking polymers having carboxyl groups can also be used.  The preferred solvent is N,N-dimethylformamide. Others which may be used include dimethyl sulphoxide, tetrahydrofuran, tetramethyl urea, N,N-dimethylacetamide, N-methyl-2-pyrrolidone and g -butyrolacetone. These solvents may be blended with water-miscible organic liquids such as ketones, e.g. methyl ethyl ketone. Polyurethane elastomers which may be used as components of the copolymer solution are prepared by chain-extending the reaction product of a polyalkylene-ether glycol and an organic diisocyanate with a compound having two active hydrogen atoms attached to amino nitrogen atoms.  These elastomers can be made from a prepolymer (or "capped dimer") obtained by heating the glycol mixed with the diisocyanate until a prepolymer is formed having terminal -NCO group, or by reacting the diisocyanate with a molar excess of the glycol, and capping the product by reacting it with more diisocyanate. Polyalkyleneether glycols which may be used in making the prepolymers include polyethyleneether glycol to polydecamethyleneether glycol. Diisocyanates which may be used in forming the prepolymers include tolylene-2, 4-diisocyanate, tolylene-2, 6-diisocyanate, m-phenylene diisocyanate, bisphenylene-4, 41-diisocyanate, naphthalene-1, 5-diisocyanate, tetramethylene-1, 4-diisocyanate, hexamethylene-1, 6-diisocyanate, decamethylene-1, 10-diisocyanate, cyclohexylene-1, 4-diisocyanate, methylene bis(4-cyclohexylene) isocyanate and tetrahydronaphthalene diisocyanate. The chain extending compound may be hydrazine (which is preferred), a substituted hydrazine or a primary or secondary diamine.  Examples are dimethyl piperazine, 4-methyl-m-phenylene diamine, m-phenylene diamine, and 4,41-diaminodiphenyl-methane. Specification 849,155, U.S.A. Specifications 2,395,017, 2,724,707, and 3,067,483 are referred to.ALSO:Vapour-permeable microporous coatings are produced by forming a coating of a water-insoluble copolymer containing carboxyl groups on the polymer chain, with or without a proportion of a vinyl chloride polymer or a polyurethane elastomer which may exceed the proportion of the copolymer, from a solution of the copolymer (and other polymer if employed) in a water-miscible solvent therefor, the solution containing also an oxide of a polyvalent metal, bathing the coating with water or an equivalent inert liquid to coagulate the copolymer and remove the solvent, and curing and drying the coating produced.  The solution of the copolymer may also contain sulphur. The copolymer may be derived from two or more monomers, at least one of which is a conjugated diene having 4-9 carbon atoms in the molecule, and at least one of which is a carboxylic acid containing ethylenic unsaturation at which polymerization can take place.  The copolymer may be a rubber ter-polymer of a butadiene-1,2 hydrocarbon, acrylonitrile or a substituted acrylic nitrile, or acrylic acid or a homologue or a -substitution product thereof.  The solution may contain a vinyl chloride polymer in a weight ratio to the copolymer of up to 50 : 50.  The solution may be brought to the verge of gelling before mixing it with water or an equivalent inert liquid. The solution may be applied as a coating to a substrate of a flexible porous fibrous material or of a smooth surfaced impervious material from which it may be subsequently stripped.  The copolymer may be partially cured by heating with water or an equivalent inert liquid to a temperature above normal room temperature.  The copolymer may contain residual unsaturation and the solution may contain sulphur and after partial curing the coating may be heated until the copolymer is fully cured.  An "equivalent" inert liquid is defined as one which is (a) a non-solvent for the copolymer and any other polymer which may be present in the solution; (b) miscible with water and the organic solvent in which the copolymer is dissolved; (c) chemically inert to all the constituents of the film-forming solution at the bathing temperature.  Examples of suitable liquids are ethylene glycol, glycerol, glycol monoethyl ether, hydroxyethyl acetate, and water-miscible alcohols such as t-butyl alcohol.  The preferred polyvalent metal oxide is zinc oxide, but oxides of calcium, magnesium, tin, dibutyl tin, lead, barium, cobalt or strontium known to be suitable for cross-linking polymers having carboxyl groups can also be used.  The preferred solvent is N,N-dimethylformamide.  Others which may be used include dimethyl sulphoxide, tetrahydrofuran, tetramethyl urea, N,N-dimethylacetamide, N-methyl - 2 - pyrrolidone and g  - butyrolacetone.  These solvents may be blended with water-miscible organic liquids such as ketones, e.g. methyl ethyl ketone.  Polyurethane elastomers which may be used as components of the copolymer solution are prepared by chain-extending the reaction product of a polyalkyleneether glycol and an organic diisocyanate with a compound having two active hydrogen atoms attached to amino nitrogen atoms.  These elastomers can be made from a prepolymer (or "capped dimer") obtained by heating the glycol mixed with the diisocyanate until a prepolymer is formed having terminal -NCO group, or by reacting the diisocyanate with a molar excess of the glycol, and capping the product by reacting it with more diisocyanate.  Polyalkyleneether glycols which may be used in making the prepolymers include polyethyleneether glycol to polydecamethyleneether glycol.  Diisocyanates which may be used in forming the prepolymers include tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, m-phenylene diisocyanate, bisphenylene - 4,41 - diisocyanate, naphthalene-1,5-diisocyanate, tetramethylene-1, 4-diisocyanate, hexamethylene-1,6-diisocyanate, decamethylene-1,10-diisocyanate, cyclohexylene-1,4-diisocyanate, methylene bis(4-cyclohexylene isocyanate and tetrahydronaphthalene diisocyanate.  The chain extending compound may be hydrazine (which is preferred), a substituted hydrazine or a primary or secondary diamine.  Examples are dimethyl piperazine, 4-methyl-m-phenylene diamine, m-phenylene diamine, and 4,41-diamino-diphenyl-methane. Specification 849,155 and U.S.A.  Specifications 2,395,017, 2,724,707 and 3,067,483 are referred to.